model.php

public function getModelRepresentation()
{
    switch ($this) {
      case instance of Mention:
          if ($this->mentionable instanceof Comment) {
             return $this->mentionable->commentable;
          }
             return $this->mentionable;
          break;
      case instance of Comment:
          return $this->commentable;
          break;
      case instance of Like:
          return $this->likeable;
          break;
      default:
          return $this;
    }
}